1. Field of the Invention
The present invention relates to a liquid jetting apparatus which jets a liquid from nozzles and a head cartridge which is used in the liquid jetting apparatus.
2. Description of the Related Art
In image forming apparatuses which form images on recording mediums such as recording papers, an image forming apparatus which jets, on recording mediums, an authentication ink such as an ink which includes DNA is available. For example, in an image forming apparatus described in Japanese Patent Application Laid-open No. 2005-125572, DNA which is synthesized in a DNA synthesizer, and an ink as a coating material are mixed in a DNA ink mixing chamber, and the DNA ink is jetted from an ink-jet head. Furthermore, in an image forming apparatus described in Japanese Patent Application Laid-open No. 2005-125572, DNA of a different type is synthesized for each validity period in the DNA synthesizer, and before supplying this DNA ink to the DNA ink mixing chamber, cleaning of the DNA ink mixing chamber is carried out by discharging the ink remained in the DNA ink mixing chamber.
However, in the image forming apparatus described in Japanese Patent Application Laid-open Publication No. 2005-125572, the DNA ink in the DNA ink mixing chamber is not removed completely just by discharging the ink in the DNA ink mixing chamber, and there is a possibility that the DNA which is supplied to the DNA ink mixing chamber subsequently and the DNA which is remained in the DNA ink mixing chamber are mixed. Moreover, if the different DNAs are mixed, there is a possibility that the validities (expiry dates) are wrongly identified when the DNA ink jetted from the ink-jet head is analyzed. Here, cleaning the DNA ink mixing chamber in addition to discharging the ink in the DNA ink mixing chamber may be taken into consideration as a cleaning operation which is to be carried out before supplying a different DNA to the DNA ink mixing chamber. However, in this case, a mechanism for cleaning the inside of the DNA ink mixing chamber is necessary, and a structure of the entire apparatus becomes complicated.
As it has been described above, a problem which arises due to mixing of inks when the ink to be used differs from an ink used previously, is not limited to a case in which a DNA ink is used. For example, a similar problem arises in a case in which physical properties change upon a chemical reaction when the ink to be used is mixed with the ink which has been used previously. Whereas, the ink-jet head has a plurality of liquid jetting systems (a plurality of channel systems which are mutually independent, as channel systems from a common ink chamber up to nozzles via pressure chambers), but the problem of mixing of inks does not arise in all the liquid jetting systems.